Can irradiance maps and light cache maps be reused?

[mlchai31]

Hi all,

I am always required to render A3 size printouts.
So I set my render size to w3360 x h2310 at 210dpi.

Can I reuse the irradiance maps and light cache maps that I
render in 640 x 480 resolution, so as to save time?


Thanks for any help.
Mlchai31

[jacksc02]

you could but it would look like S#$% unless you had done it with extremely high settings with LOTS of samples for the light cache.

[natty]

as a general rule you can say render 800 x 600, save the maps and then render from those maps but double the render size. But increase your AA a little because it tends to blur the irr map a little, but it works fine.

[DaForce]

yeah, so you could get away with using an IR map from a 1680 x 1155 render.

But any lower than that and you will start loosing alot of quality.

[gilicom]

i find it faster to render on -5 -3 settings on 3000+ * 2000+ then to save the irr map on half size and reuse it since you'll need higher settings(-3,-1) prob.

[glyph]

could someone clarify this for me please:

reusing (and upscaling) irmaps is ok (I've been doing that myself for ages)..

but do lightcache maps scale the same way or are they more picky?

[DaForce]

Light cache is resolution Independant.
So you can make a render of 4x3 pixels and save the light cache and use it in a 4000x3000 render and it will look the same.
It will also take the same time to calc, either the 4x3 render or the 4000x3000 render

But what you may not no is that the LC info is stored in the IR map as well.

So you can make a render of 800x600 using IR/LC and the IR map and reuse it in a 1600x1200 render with 2nd bounce turn off and it will look fine, as it has both the IR and LC info within it (in a sense)

[Clifton Santiago]

Daforce: If that is the case, why is there an option to save and re-use the LC?

[TRGraphics]

I'm curious about that too!

[Da_elf]

It is the case. even vlado has said lightmaps get saved with irradiance maps. as to why there is a save options, its there just incase there is someone wishing to use LC in both primary and secondary. Im not saying its a normal thin for someone to do however just incase someone wanted to do it. the possibility is there and someone would whine and moan if it wasnt there. Arnt there some people who use LC and QMC?

[Clifton Santiago]

So if I understand what you're saying, when I do a IR/LC pre-calc pass, I only need to save and re-use the IR, and not both IR and LC. That will save a step...

[Da_elf]

correct. then when you render you can set seconddary bounce to none and use the irradiance map only. this will save how ever much ram the LC would have used being loaded up for render

[DaForce]

Yep that is correct... have confirmed myself recently.

The other option why saving LC is there is alot of the guys here now use QMC/LC for there interiors... so saving the LC is a must.

But if you us IR for your first bounce... then once that is saved you can turn off the 2nd bounce. Renders times are the same but it does save that extra step.

[flipside]

There's no reason why you cannot use a 800*600 rendered ir map on a 3200*2400 image for example. If your GI looks good on the 800*600 (nice small GI shadows), then it will look as good on the 3200*2400 image (but scaled of course, so what looked nice & small on the 800px is now bigger, so you may notice the artifacts more).

You can do this in one pass too, just set render size to 3200*2400 and lower the min/max both by 2 (you double the resolution twice, so you can lower the min/max twice). This will give you the same ir map as on the 800*600 image.

If you use LC for glossy rays option, you also need to save and load the LC map.

There's a great tutorial in the help files on saving and reusing GI info, which explains everything in detail.

[Marshall_Craft]

well, i don't know if anyone else is/was having this problem, but i had to calculate the LC in a first pass, THEN calculate the IR map in a separate pass, and THEN i could do a render pass with just IR map for primary (no LC for glossy.) i think some of it may have been due to not having exployed the 3Gb switch, but in general i have had fewer crashes when separating out my GI into passes.

- Alex